Process for filling liquefied gas vessels

ABSTRACT

A process and mechanism for filling liquefied gas vessels to increase the filling speed and decrease the build-up of pressure within the vessel by forming the incoming liquid into a solid stream with a controlled velocity to stir the contents of the vessel and mix the incoming liquid with the liquid already in the vessel; the mechanism for controlling the velocity of the incoming liquid comprising a check valve which opens as the liquid gas flow rate increases and closes as the flow rate decreases to provide a lower limit on the velocity of the liquid gas entering the vessel without an excessively high velocity at high flow rates.

United States Patent 1191 Garretson PROCESS FOR FILLING LIQUEFIED GAS VESSELS 1451 July 31,1973

Primary Examiner.l0hn Petrakes Assistant ExaminerFrederick R. Schmidt [76] Inventor: Owen L. Garretson, PO. Box 108,

Farmington, N. Mex. 8 7401 Attorney-James Snead [22] FilCdZ July 20, 1970 57 ABSTRACT [21] Appl. No.: 56,334 A process and mechanism for filling liquefied gas vessels to increase the filling speed and decrease the build- 52 us. (:1. 141/5, 137/5123 P W the vessel by the f" 51 1m. (:1. B651) 31/00, B67c 3/02 f 3 Stream a [58] Field of Search 141/1-5, the the vessel and the H285, 286, 290 293, 294, 295 296; liquid with the liquidflalreaidy in the lvessel; the mlecha 239/11; 221; 137/512 5123; 138/37 38, msm for control mg e ve ocrty oft e1ncom1 ng qu1 39 40 comprising a check valve which opens as the liquid gas 1 flow rate increases and closes as the flow rate decreases [56] References Cited to tprovidfha lowerllirr rtittl ontthe velocity (if ttllre rliiquild gas UNITED STATES PATENTS 2:1 tteirgrtrligflo v1: :32: w1 ou an excessive y 1g ve oc1 y 1,647,873 10/1927 Lockwood 137/512 2,522,406 9 1950 Smith 137/5123 2 Clams, 6 Drawing Figures I l 1 N L 18 l I 25 22 I 19 2 I l c :a 14 1 Q 1 4 i 24- a l 14 I 32 32 fi p 29 2 F 37 27 1 l t, 10 it 2/ 12 1 1:

3 Sheets-Shoot 1 Patented July 31, 1973 OWEN L. GARRETSON INVENTOR BY 4 Z 9 ATTQRNEY Patented July 31, 1973 3,749,141

5 Sheets-Sheet 2 OWEN L. GARRETSON INVENTOR ATTORNEY Patented July 31, 1973 3,749,141

3 Sheets-Sheet \iij IE 5 OWEN L. GARRETSON INVENTOR ATTORNEY PROCESS FOR FILLING LIQUEFIED GAS VESSELS BACKGROUND OF THE INVENTION A. Field of the invention This invention lies in the field of liquefied gas filling processes and valving mechanisms for controlling the velocity of injection of liquefied gas into vessels so as to achieve an optimum filling rate with the least possible pressure rise and to minimize the load on the filler pump.

B. Description of the Prior Art There has in the prior art been a long standing need for a process and a device to fill liquefied gas vessels such as propane or butane tanks or pressurized liquid fertilizer tanks such as those containing anhydrous ammonia so as to achieve the optimum filling rate and not increase the vapor pressure within the tank to the danger point or create a back pressure on the filler pump which impedes the filling process.

It is known that at the time of refilling, pressure vessels containing liquefied gases usually have a relatively large percent of the container volume filled with vapor. When the container is being filled the incoming liquid reduces the volume of the vapor space in the container so that the vapor must either be compressed with a resulting rapid increase in vapor pressure and temperature or it must be absorbed into the incoming liquid. If it is absorbed into the incoming liquid the temperature of the liquid itself is raised due to the latent heat of vaporization of the vapor absorbed, and this again raises the pressure in the vessel. The temperature and composition of the surface layer of the liquid in the tank is determinative of the pressure created when there is vapor-liquid equilibrium, and the pressure rise in the container being filled is greatest if the new liquid added is allowed to float on the surface of the liquid already in the container. Additionally the vessel walls above the liquid level are normally at a higher temperature than that below the liquid level when a vessel is filled during daylight hours. As the rising liquid contacts the warmer walls during the filling operation the liquid is warmed and additional vapor released to thus increase the vapor pressure. The liquid remaining in a vessel at the start of refill usually is of a composition that produces less pressure at any given temperature than does the fresh incoming liquid. If the incoming liquid is mixed with it, the tank pressure is less than if the fresh liquid is allowed to collect on top.

Existing filler devices do not solve the problem of the rapid increase in pressure in the container during the filling operation. Some devices in the prior art spray the liquid into the vapor space and unto the surface of the liquid already in the container. The temperature of the sprayed liquid is increased by the vapor absorption, its density iS reduced by the increase in temperature and it floats on the surface of the liquid already in the container, thereby raising the interior pressure in the vessel. This high pressure causes the vapor to become more dense, requiring additional vapor absorption during the filling operation and compounding the pressure rise problem.

Other prior art devices inject a solid stream of liquid into the vessel through an orifice of fixed size. This type of filler valve is not adequate to solve the problems due to the fixed nature of the valve orifice. If the crosssection of the flow area of the stream through the valve is large, the flow velocity is low and very little mixing of the liquid in the container is accomplished. If, on the other hand, the cross-section of the orifice is small its flow resistance causes a large back pressure on the filler pump to be created at normal or high flow rates which impedes the pumping efficiency of the filller pump.

BRIEF DESCRIPTION OF THE INVENTION It is therefore an object of this invention to provide a process for filling liquefied gas vessels at the optimum rate while maintaining a safe vessel pressure and a low back pressure on the filling pump.

Another object of this invention is to provide a process for filling liquefied gas vessels whereby the velocity of the incoming liquid is controlled in accordance with varying liquid flow rates.

A further object of this invention is to provide a process for controlling the velocity of input liquid into a liquefied gas vessel within the range of flow rates of the filler pump and to form the incoming liquid into a solid stream into the vessel so as to mix incoming liquid with that already in the tank and achieve optimum filling rate and reduce pressure rise during the filling operation.

A further object of this invention is to provide a liquefied gas vessel filler valve whichh automatically adjusts the velocity and composition of the incoming liquid by providing a control means on the filler valve to vary the flow cross-section area to maintain a reasonably .constant liquid velocity with changes in its flow rate and to form the incoming liquid into a solid stream.

A further object of this invention is to provide a filler valve for liquefied gas vessels wherein the size of the valve orifice varies with variation in the flow rate of the incoming liquid.

Other objects and advantages of this invention will become apparent as the same is better understood by reference to the following specification and accompanying drawings wherein:

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional view ofa liquefied gas filler valve incorporating one embodiment of the invention.

FIG. 2 is a cross-sectional view of the device shown in FIG. 1, taken along lines 22 of FIG. 1.

FIG. 3 is a cross-sectional view of another filler valve incorporating a second embodiment of the invention.

FIG. 4 is a cross-sectional view of the device shown in FIG. 3, taken along lines 44 of FIG. 3.

FIG. 5 is a cross-sectional view of a third filler valve incorporating a third embodiment of the invention.

FIG. 6 is a cross-sectional view of a fourth filler valve incorporating a fourth embodiment of the invention.

DETAILED SPECIFICATION Throughout the specification the filler valve assembly is designated by a numeral 10 in each embodiment. There are many embodiments whichincorporate the concept of this invention. The basic point in common to all embodiments is that the lower check valve of the filler valve assembly has a control means thereon for directing the liquid flow and for varying the size of the valve orifice which in turn varies its degree of opening as the flow rate of input liquid varies.

Referring now to the embodiment of the invention shown in FIGS. 1 and 2, the outer housing of filler valve assembly comprises two parts, those being filler valve casing 11 and-a check valve control housing 12. The top 13 of filler valve housing 11 is threaded to allow attachment of a standard filler hose or of a cover when the valve is not in use. The bottom 14 of filler valve housing 11 may be threaded inside and out to allow threaded insertion of filler valve 10 into a pressure vessel and to allow check valve control housing 12 to be removably attached to bottom 11. Control housing 12 could be affixed to bottom 14 of filler valve housing 11 by other suitable means, such as welding or sweat fitting.

The upper and central portion of check valve housing 1 l surrounds a first check valve 16 which consists of a first check valve seat 17 which is threadedly engaged within the interior of housing 11, a flexible check valve sealer 18, a check valve 19, and a helical spring which urges check valve 19 into engagement with flexible check valve sealer 18. Obviously flexible check valve sealer 18 may be attached to check valve 19 or it may be attached to the first check valve seat 17. The only requisite is that upon closure of check valve 19 flexible sealer 18 is interposed between valve seat 17 and check valve 19 to form a seal against passage of fluid. First check valve 16 is a standard check valve and is to be found in several of the liquified gas filler valves of the prior art. Its disclosure here is for the purpose of clarifying the operation of this particular invention.

One end of helical spring 20 seats on check valve 19 as shown in FIG. 1 and the other end is seated upon a shoulder 21 Formed in support member 22 which consists of a plurality of radially extending arms 23 extending from a hollow cylindrical sleeve 24 which surrounds and guides valve shaft 25 during the operation of first check valve 16. A cross-sectional view of support member 22 is shown in FIG. 2.

Check valve control housing 12 threadedly engages the lower portion of check valve housing 11 and surrounds second check valve 27. Second check valve 27 comprises a conical valve seat 28, a check valve 29 and a valve control spring 30. One end of valve control spring 30 engages the lower portion of movable valve 29 and at its other end it is seated within lip 31 of check valve control housing 12. Thus the movement of valve 29 is controlled by the force of helical valve control spring 30. A plurality of relief holes 37 may be provided in check valve control housing 12 so that during the operation of the device excess fluid may flow from relief holes 37 after valve 29 is fully open. The beveled sides 32 on movable valve 29 are machined to match the beveled surface 33 of conical valve seat 28 so as to close the orifice of second check valve 27 and to direct the exiting liquid toward the axis of the valve orifice to form a solid stream.

It should be noted here that the entire valve is basically cylindrical along its longitudinal axis and the cross-sectional view shown is taken along the longitudinal axis of the filler valve 10. Thus valves 19 and 29 are circular in the plane perpendicular to the plane of the drawings so as to entirely engage the valve seats 17 and 33 respectively.

In operation, filler valve 10 is threadedly engaged by means of threads 14 in a liquefied gas vessel such as a propane tank. Normally the filler valve would be attached to the tank when it is manufactured or at a later date when the tank is empty. Liquefied gas is then injected into the top of the filler valve through first check valve 16. The force of the incoming liquid opens valve 19 to allow the liquid to pass through first check valve 16 into second check valve 27. As second check valve 27 opens, the beveled sides of the valve 32 and seat 33 direct the flow of the liquid toward the longitudinal axis of the valve with the size of valve orifice varying in accordance with the flow rate of the incoming liquid. The liquid converges toward the longitudinal axis of the valve as it exits through the orifice in second check valve 27 to form a solid stream.

The velocity of the liquid through the valve orifice is a function of the size of the valve orifice and the liquid flow rate. The orifice size is controlled by the strength of helical spring 30. Thus the spring strength can be designed within limits to allow opening of valve 29 by a predetermined amount for a particular flow rate. Since the normal range in flow rate of liquefied petroleum gas pumped into a gas vessel varies fromom 20 to gallons per minute, the control spring 30 and valve orifice can be designed to provide the smallest desirable opening at the lowest flow rate and thus increase the velocity of the liquid as it passes through the orifice and to provide the widest orifice opening at the highest liquid flow rate to reduce the back pressure on the filler pump. As a part of the design criteria it must be kept in mind that the velocity of the liquid stream entering the vessel through the orifice of second check valve 27 must be sufficient to cause stirring and mixing of the incoming liquid with the liquid already present in the vessel to maintain the liquid on the surface at as low a temperature as possible and thus minimize the rise in vapor pressure within the vessel as it is being filled. In the event the flow rate of the liquid through the orifice of second check valve 27 is greater than the capacity of the valve then a portion of the liquid can exit through relief holes 37 to relieve the back pressure on the filler pump.

A second embodiment of this invention is shown in FIGS. 3 and 4. First check valve 16 is substantially the same as shown in FIG. 1. The only difference is that the lower portion of valve stem 25 has a conical point 34 which projects downwardly when first check valve 16 is open so as to be contiguous with valve seat 35 on second check valve 36 as shown in FIG. 3. A second check valve support member 38 is secured within valve housing 1 1 and no valve control housing is necessary in this modification. Second check valve support member 38 is formed as a hollow cylinder with radially extending arms which engage and support valve seat 35 by attachment to shoulder 42 and engage the interior walls of housing 11 in a suitable manner. For example as shown in FIG. 3, a recess 39 may be machined in housing 11 with the inside diameter of the recess 39 being the same as the outside diameter of support member 38. After support member 38 is inserted into recess 39 the bottom portion of housing 11 may be swedged to retain support member 38. Other suitable attachment means may be provided.

Valve seat 35 is fixedly attached to support member 38 by means of radially extending arms connecting the two members. Shoulders 41 are formed in the top portion of valve seat 35 to provide a lower seat for helical spring 20 which controls the movement of first check valve 19. A second shoulder 42 is machined into valve seat 35 to provide a lower seat for second check valve control spring 43. Second check valve control spring 43 is a helical spring. Check valve 44 is formed as a circular disc with a depressed lip 47 which engages shoulder 45 machined in valve seat 35 on its inside diameter. Shoulder 46 is machined in the inside portion of valve support member 38 to provide a seal with one side of check valve 44 when closed. The clearance between the outside diameter of check valve 44 and the inside diameter of the machined shoulder 46 is sufficiently close so that liquid passing through valve 44 is forced through the orifice between the depressed lip 47 of valve 44 and shoulder 45 on valve seat 35. Lip 47 of valve 44 aids in directing the liquid flow toward the longitudinal axis of second check valve 27.

Referring to the embodiment of the invention shown in FIG. 5, first check valve 16 is not shown since it is substantially the same as that disclosed in FIGS. 1 and 2. Second check valve 50 consists of a valve seat 51, a valve 52 and a valve control helical spring 53. A snap ring 54 is provided at the bottom of housing M to seat one end of helical spring 53 with its other end engaging valve 52. A shoulder 55 is machined in valve seat 51 and a shoulder 49 is machined into interior wall of housing 11 to engage valve 52 and close the valve orifice when the filler valve is not in use. The clearance between shoulder 49 and valve 52 is such as to allow little leakage between the members. Thus the liquid is directed toward the center of the valve as it exits through the orifice and the size of the aperature is controlled by the force of spring 53 against the flow of liquid. Valve seat 51 may be removably supported within the valve housing by any suitable means, such as radial arms 49 extending from valve seat 51 into engagement with the interior wall of the valve housing. A snap ring 49 engages the top of radial arms 48 to retain valve seat 51 within the housing.

Referring to the embodiment of the invention shown in FIG. 6, the second check valve has been modified into a pop up type valve. Again the first check valve 16 is the same as that disclosed in relation to the other embodiments of the invention and is not shown in FIG. 6. Second check valve 56 comprises a valve support member 57 secured within housing It by a plurality of spokes 58 which radiate from support member 57 and are attached to the interior wall of housing 111 by any suitable means such as a snap ring 63. A hollow is formed within support member 57 in which is seated helical control spring 59 which engages the interior of the hollow portion support 57 at one end and the rear of valve 60 at the other. A pressure passage 61 is provided through valve 60 to equalize the pressure on either side of valve 60. A first and second valve seat 62 and 63 respectively are formed, with the first being on support member 57 and the second consisting of an in ward projection of housing 11. First valve seat 62 engages a shoulder 64 machined in pop up valve 60 to form a seal therewith. Second valve seat 63 engages the conical shoulder of valve 60 to form a seal therewith. The force of the liquid flowing through the valve causes valve 60 to pop up" and emit liquid through the valve orifice with the size of the orifice varying in accordance with the flow rate of the liquid. Again beveled sides of valve 60 and valve seat 63 direct the liquid exiting from the valve orifice toward the longitudinal center thereof to form a solid stream prior to striking the liquid in the tank.

It is obvious that other types of check valves may be provided to accomplish the purposes of this invention within the normal skill of mechanics. The requisites of the valve are that they direct a substantial portion of the exiting liquid to converge at one point and form a solid stream and the velocity of the liquid is controlled so as to always be sufficiently high with variations of the flow rate of the liquid through the valve. For example a leaf spring check valve could be provided in the device if a square valve were used, or any of many other types of check valves could be designed to suit the purpose of this invention.

The process of this invention basically is that of injecting a volatile liquid intt) a pressure vessel, comprising the steps of discharging the incoming liquid through a check valve system into the pressure vessel, varying the valve flow area for the incoming liquid for variations in the flow rate and forming a large part of the incoming liquid from the valve into a solid stream so that it strikes the surface of the liquid within the tank in a solid stream so that it stirs the liquid and mixes the incoming liquid with that already in the vessel.

Experimentally the process of this invention has been used to determine the comparable results to a filling process using a standard filler valve of the prior art. In the process a 500 gallon tank of 37 inch diameter with the filler valve located at the top center of the tank was used. The tanks were refilled with 250 gallons of propane at an injection temperature of 65 F. and at the start each tank contained 175 gallons of propane with an initial pressure of 65 pounds per square inch gauge pressure and 335 F. liquid temperature. Each tank was painted the same color and the ambient temperature was F. with a hazy overcast sky. 250 gallons of propane were injected into each tank and the filling time and tank pressure were measured. It was found that a period of 285 seconds was required to fill the tank utilizing the process of this Invention whereas 309 seconds was required to fill the tank utilizing the prior art process. The tank pressure increased from 65 pounds per square inch to 107 pounds per square inch during the filling process of this invention whereas the tank pressure increased from 65 PSI to I42 PSI utilizing the prior art process. The tank pressure after filling with the process of this invention was less than the vapor pressure of the incoming liquid and 35 PSI less than the pressure when prior art process was used. The pumping rate utilizing the process of this invention was 8 percent faster than the pumping rate utilizing prior art processes with the filler pump being operated during both experiments at the same throttle setting for the engine that powered it.

Thus it can be seen that the process of this invention does in fact accomplish an increase in filling rate and a decrease in vessel pressure rise during the filling operation.

What is claimed is:

1. In a process for filling liquefied gas vessels to minimize internal pressure rise during the filling operation, the steps comprising:

Connecting the output of a source of supply of liquefied gas to the input of a liquefied gas pressure vessel:

Transferring liquefied gas from the interior of the source of supply, through its outlet, into the interior of the liquefied gas vessel through its inlet;

Directing the stream of incoming liquid toward its longitudinal axis as it passes through the inlet to thereby form it into a solid stream.

7 8 2. The process as defined in claim 1, including the reducing the restriction to flow of gas through the step of: inlet for increases in the flow rate of incoming gas; Maintaining a constant stream velocity of the gas as Whereby the gas stream entering the liquefied gas it is discharged into the pressure vessel by increasvessel tends to maintain a constant velocity with ing restrictions to the flow of gas through the inlet variations in the flow rate of the incoming gas.

for decreases in the flow rate of incoming gas and 

1. In a process for filling liquefied gas vessels to minimize internal pressure rise during the filling operation, the steps comprising: Connecting the output of a source of supply of liquefied gas to the input of a liquefied gas pressure vessel: Transferring liquefied gas from the interior of the source of supply, through its outlet, into the interior of the liquefied gas vessel through its inlet; Directing the stream of incoming liquid toward its longitudinal axis as it passes through the inlet to thereby form it into a solid stream.
 2. The process as defined in claim 1, including the step of: Maintaining a constant stream velocity of the gas as it is discharged into the pressure vessel by increasing restrictions to the flow of gas through the inlet for decreases in the flow rate of incoming gas and reducing the restriction to flow of gas through the inlet for increases in the flow rate of incoming gas; Whereby the gas stream entering the liquefied gas vessel tends to maintain a constant velocity with variations in the flow rate of the incoming gas. 